1. Field of the Invention
The present invention relates to an electronic position sensor having a guide housing accommodating a magnetic component.
2. Description of the Related Art
Published German patent application document DE 10 2006 059741 A1 relates to a modularly developed sensor carrier design. The sensor carrier design includes at least one base housing and at least one sensor carrier module produced separately from it. The sensor carrier module is made of molding-compatible material, and is able to be fastened mechanically on the base housing of the sensor carrier construction.
For applications in a motor vehicle, especially for position sensors for a transmission control system, the sensors are installed in electronics modules, in an integrated manner. In automatic transmissions, for example, inserted sensors have to be designed for the demanding operating conditions that prevail there. They have to withstand environmental temperatures between −40° C. and +150° C., and also withstand aggressive environmental medium transmission oil (ATF=automatic transmission fluid), high mechanical stresses up to 30 g and have to resist metallic abrasion and particle formation in the transmission.
The resistance to media and temperatures in these applications is ensured by oil-resistant packaging of the electronics, as well as the use of high-temperature printed circuit boards. Different physical measuring principles are used, based on complex requirements from different transmission topologies as well as insertion space and functional requirements. Linear position detection may take place, for instance, based on Hall switches. In this connection, four digital Hall switches are used, which are positioned on a printed-circuit board, in such a way that they record the magnetic coding of a linearly displaceable, multi-polar permanent magnet. A magnetic slider is connected to the linearly operated selector slide, a hydraulic slide in the transmission control plate or a parking lock cylinder.
Besides the Hall switches, there are resistors located on the printed-circuit board for the implementation of diagnostic functions and EMV capacitors.
The sensor electronics are protected by a sealed, oil-resistant epoxy resin molding from the effects of transmission oil. In an automatic transmission having manual shifting, also referred to as M-shifting, the position sensor detects the positions of the selector slide P, R, N, D, 4, 3, 2, as well as the intermediate ranges. These are output to the transmission control in the form of a 4-bit code. For safety reasons, the coding of the position setting is performed in one step, that is, a bit change is always required up to the detection of a new position. Simple bit changes caused by a malfunction are able to be detected as faulty, using a plausibility observation. The design of such position sensors for transmission control is known from the publication “Sensoren im Kraftfahrzeug” (Sensors in the Motor Vehicle), Robert Bosch GmbH, Edition 2007, Fachwissen Kfz-Technik, Elektrik und Elektronik für Kfz, ISBN-10 3-7782-2031-4, pages 136-138.